Seeds are amazing. These small packages contain everything needed to make a whole plant, and many also contain tiny sensors to tell them if the time is ripe for germination. Among those sensors is phytochrome, a pigment that is sensitive to certain wavelengths of red light.
Who cares? You will if you sow these seeds and cover them with soil. Seeds that need light, and often they are smaller seeds, will not germinate if they are buried too deeply. When a seed is struck by sunlight (or light from a regular incandescent bulb), the phytochrome changes. If the seed has warmth, moisture, and oxygen, the change in the phytochrome breaks the seed’s dormancy and allows germination. If the environment is not to the seed’s liking, the phytochrome slowly changes back and the seed waits for another blast of light when conditions are better.
Among seeds that need light to germinate are ageratum, California poppy, gaillardia, coleus, columbine, love-in-a-mist, snapdragon, Shasta daisy, strawflower, sweet alyssum, and sweet rocket. You can’t tell by looking, so following seed-package instructions is always a good idea.
Seeds vary in the texture and thickness of their seed coat, which affects how fast water can penetrate. The presence of water in turn allows germination.
Some plants, among them flowers like morning glory, lupine, and moonflowers, have rather thick seed coats. To get them going, suppliers often recommend that they be scarified — nicked, scraped, or chipped — to create tiny breaks in the seed coat. With these cracks, moisture can penetrate easily and the plant will spring to life more quickly.
What happens if there’s no human around to do this job? Nature has methods, but they take longer. Thick seed coats are eventually worn away by soil fungi, bacteria, the elements, or a trip through the digestive system of a bird or other animal.
Good seed germination depends on more than adequate light and moisture. It’s also affected by soil temperature.
Different plants have different needs in the temperature department, but almost all of them will do okay at 70º to 75ºF.
Because cold tap water can lower the temperature considerably, use tepid. And don’t forget that temperatures warm enough to keep the soil in the 70s will probably make the air above the soil too warm for the seedlings when they do come up. The solution? Either supply bottom heat only, using a gardener’s heat mat or heating cable, or put the flats on top of the fridge until about half of the seeds have sprouted and then move them to the windowsill.
Chances are good you will have leftover seeds when you’re done planting annuals. Not all of them are worth saving; asters and larkspurs, for instance have very short storage lives. But most will be perfectly usable next year if they are stored dry, cool, and dark.
Date each packet and reseal it with tape. Put the packets in a glass jar with a screw cap, or in a thick-plastic freezer-storage bag. Put the jar or bag in a cool place or in the freezer (away from the coils if it a self-defrosting model). When you’re ready to use the frozen seeds, remove the packets from the jar or bag and spread them out flat before letting them thaw, so they don’t get wet from condensation.
A few seeds will die, no matter how carefully they are stored, so plant saved seed a little more thickly to allow for the reduced germination rate.
by OCMGA Master Gardener Vicki Schilleman